In modern internal combustion engines, devices for variably setting the timing of gas exchange valves, also known as camshaft adjusters, are used to be able to variably change the phase position of a camshaft relative to a crankshaft in a defined range of angles between a maximum advanced position and a maximum retarded position. The cams of the camshafts commonly contact cam followers, for example, bucket tappets, rocker arms, or finger levers. If a camshaft is set in rotation, the cams roll on the cam followers that, in turn, actuate the gas exchange valves. The position and the shape of the cams thus define both the opening period and also the opening magnitude, but also the opening and closing times of the gas exchange valves.
The angular displacement of the camshaft with respect to the crankshaft for achieving optimized timing for different rotational speeds and load states is called camshaft adjustment. One structural variant of a camshaft adjuster operates, for example, according to the so-called oscillating engine principle. Here, a stator and a rotor are provided that lie coaxially and can move relative to each other. The stator and the rotor together form pairs of hydraulic chambers. Each chamber pair is hereby bounded by webs of the stator and divided by each vane of the rotor into two pressure chambers that act against each other and whose volumes are changed in opposite directions by a relative rotational movement of the rotor relative to the stator. In the maximum adjustment position, each vane contacts one of the edge-side webs of the stator. The relative rotational movement of the rotor is realized by an adjustment of the vane in that a hydraulic medium or pressurized medium, such as oil, is introduced by means of pressurized medium channels into one of the pressure chambers of the chamber pair and presses away the vane. The pressurized medium channels open on both sides of each vane, so that the hydraulic medium is guided into the respective pressure chamber.
For controlling flows of pressurized medium for camshaft adjusters, hydraulic control valves in the form of multiple-path gate valves are normally used. As essential components, they comprise a valve housing and a control piston that is held so that it can move in the axial direction in a housing cavity and is activated by an actuator, typically an electromagnet with a tappet.
In one common construction, such control valves are switched as so-called central valves that are used in a central hole of the rotor of a camshaft adjuster. The valve housing of such a central valve is provided with a thread by means of which the valve housing can be screwed into a corresponding threaded hole of the camshaft, in order to connect the rotor to the camshaft in a rotationally locked way. A feed of pressurized medium to the pressurized medium connection and a discharge of pressurized medium from the discharge connection of the control valve are performed through the rotor and the camshaft, respectively. The feed of pressurized medium is performed in the radial direction by means of a feed connection. By means of two work connections on the valve housing, the pressurized medium is introduced alternately into the opposing chambers of a chamber pair. Depending on the position of the control piston, one of the chambers is connected to the feed connection by means of one of the work connections and is filled with the pressurized medium. At the same time, the opposing chamber communicates with a discharge connection on the control valve by means of the work connection allocated to it and is emptied in this way.
When the internal combustion engine is operating, the camshaft can be subjected to changing moments that are transferred via the pressure chambers as pressure shocks to the hydraulic system of the camshaft adjuster. To prevent a forwarding of such pressure shocks, non-return valves that can be unlocked hydraulically are used in the pressurized medium feed of the camshaft adjuster.
A control valve with an integrated, flat non-return valve is described in DE 10 2008 004591. A hollow pressurized medium insert that has an outer diameter adapted to the inner diameter of the housing is inserted in a valve housing of the control valve. The pressurized medium insert comprises a sleeve-shaped insert section with a structural section that is shaped on the housing side and is provided on the end with an axial support ring. The support ring is held within an axial holding collar that is shaped on a seating surface body. The holding collar is bent radially inward on its free end and engages behind the support ring, wherein the three components of the seating surface body, closing element, and pressurized medium insert are fixed in their relative axial position. An end surface of the axial support ring comes into contact with a closing element that contacts, on its side, against a seating surface shaped by the seating surface body. The plate-shaped closing element has a plurality of openings that are constructed such that a central closing part spring-mounted by means of multiple spring tabs is shaped for closing a valve opening. The openings here surround the closing part in a spiral shape. A ring filter is also installed in the pressurized medium line upstream of the non-return valve.
Such a multiple-part construction of the pressurized medium insert, the non-return valve, and the filter leads to increased handling costs and is associated with multiple processing steps in the installation of the individual components of the control valve.